1. Field of the Invention
The present invention is a chemical process for the isomerization of the xcex945(10),9(11)-double bonds in a steroid to the corresponding xcex944,9-isomer.
2. Description of the Related Art
J. Am. Chem. Soc., 73, 4133 (1951) discloses isomerization of a xcex948(9)-12-one steroid to the corresponding xcex949(11)-12-one steroid using hydrochloric acid in methanol.
J. Chem. Soc., 367 (1950) discloses isomerization of xcex945(10)-3-one steroid to the corresponding xcex944(5)-3-one steroid using sodium ethoxide.
Tetrahedron, 22, 2837 (1966) discloses isomerization of a xcex945(10)-3-one steroid to the corresponding xcex944(5)-3-one steroid using potassium hydroxide in ethanol.
U.S. Pat. No. 3,052,672 discloses isomerization of xcex945(10),9(11)-3-one steroid to the corresponding xcex944(5),9(10)-3-one steroid using perchloric acid in acetic acid.
These documents while disclosing isomerization of double bonds leading to conjugation with the carbonyl group in six-membered rings in steroidal compounds do not use a phosphorous containing acid.
Disclosed is a process for the preparation of a xcex944,9-steroid of formula (II) 
where R17 is:
(1) xe2x95x90O;
(2) xcex1-R17-1:xcex2-R17-2 where one of R17-1 and R17-2 is:
(a) xe2x80x94OH,
(b) xe2x80x94Oxe2x80x94Si(R17-2a)3 where R17-2a are the same or different and are C1-C6 alkyl or phenyl,
(c) xe2x80x94Oxe2x80x94COxe2x80x94R17-2b where R17-2b is:
(i) C1-C6 alkyl,
(ii) phenyl,
(d) xe2x80x94Oxe2x80x94R17-2b where R17-2b is as defined above, and the other of R17-1 and R17-2 is xe2x80x94H; which comprises
(1) contacting a xcex945(10),9(11)-steroid of formula (I) 
where R17 is as defined above, with a phosphorous containing acid selected from the group consisting of phosphoric acid, polyphosphoric acid, metapahosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, tetrametaphosphoric acid, hypophosphoric acid, orthophosphoric acid or an acid containing phosphorus which is generated in situ.